1. Field
Exemplary embodiments of the present invention relates to an information processing technique for realizing a natural augmented reality effect by displaying, in a real space which is visible to a user, an image in which a virtual object image is superimposed on a photographed image, and more particularly to an information processing technique for causing a virtual object to appear or changing the virtual object so as to allow a user who is experiencing a natural augmented reality to maintain his/her interest enhanced.
2. Description of the Background Art
There are many games which are realized by programs being executed by dedicated game apparatuses or general-purpose computers. In many of such games, stages having different difficulty levels are provided so as to enable a user to continuously have an interest in the game, and the user is sequentially guided from a stage having a lower difficulty level to a stage having a higher difficulty level. In such a game, when a user clears a certain stage, and advances to a subsequent stage, a predetermined image is displayed on a game screen as shown in, for example, FIG. 9 of Japanese Laid-Open Patent Publication No. 2007-222310 (hereinafter, referred to as Patent Document 1). According to Patent Document 1, the predetermined image is displayed on the screen in order to perform a process for reading data necessary for the subsequent stage.
However, if a game screen presenting a realistic scene shifts to the predetermined image (single color image representing “Now loading . . . ” in Patent Document 1) as in the game apparatus disclosed in Patent Document 1, a user is prevented from being involved in a game, and a user may become less interested in the game. Therefore, it is important to display a game screen which does not prevent a user from being involved in the game even when a stage shifts to another one.
On the other hand, a so-called augmented reality system is realized which displays, as if an object exists in a virtual space, an image in which a virtual object image is superimposed on a real world (a real space or a real environment) that is visible on a screen of a display device. The augmented reality system provides a technique for displaying a virtual object in a real world, and displays the virtual object, without causing unnaturalness, by, for example, superimposing a previously generated image of the virtual object on a real space photographed by a camera. When such an augmented reality system is applied to a hand-held game apparatus, a game can be realized in which, for example, a target used for a shooting game is positioned as a virtual object in a real world the image of which is taken by an imaging unit of a game apparatus, and a user shoots at the target which is the virtual object.
Also in some of such shooting games realizing the natural augmented reality effect, a stage having a lower difficulty level shifts to a subsequent stage having a higher difficulty level when the stage having the lower difficulty level is cleared, as described above. In this case, if the game screen shifts to a predetermined screen for switching the stages, although a virtual object can be switched (to a target of a higher difficulty level), a user is prevented from being involved in the game, as described above for a typical game. Therefore, the inventors of the present invention have found that there is a great problem associated with a display method for switching stages in games to which the augmented reality system is applied.
Specifically, in a game to which such an augmented reality system is applied, a field of a stage is a real world which is visible to a user on a screen of a display device. Virtual objects such as characters and targets are superimposed and displayed on such a real world. If a virtual object representing a target for a certain stage is directly switched to a virtual object representing a target for the subsequent stage, the virtual objects are suddenly switched in a state where the real world remains unchanged. In this case, however, it is difficult to realize a natural augmented reality, and a user may feel greatly unnatural.
Further, in a typical game, a character operated by a user may be guided from a field (for example, a forest) of a certain stage to a field (for example, a town) of a subsequent stage. However, in a game to which the augmented reality system is applied, since the field depends on a real world, such a guidance cannot be realized.
In order to overcome the problems, in a game to which the augmented reality system is applied, it is important not only to enable a user to be continuously involved in the game but also to start a new stage by switching virtual characters so as to realize a natural augmented reality. However, neither the game apparatus disclosed in Patent Document 1 nor known techniques can solve these problems.